Distinguishing edema vs scar in the rabbit subglottis using optical coherence tomography

Abstract

Problem: In neonates, subglottic stenosis is a tremendous problem related to prolonged enotracheal intubation. Despite the use of diagnostic endoscopy, differentiating between edema, scar, or neocartilage formation remains a challenge. Optical Coherence Tomography (OCT) is an imaging modality that uses light to produce high-resolution cross-sectional images in tissue. Using an ex vivo rabbit laryngotracheal model, we evaluate the efficacy of OCT to differentiate between several simulated subglottic pathologies. Methods: Seven laryngeal-tracheal complexes were harvested from freshly sacrificed rabbits. The specimens were divided into 4 groups: (1) control; (2) submucosal collagen injection (simulating scar formation); (3) dehydration/hydration (simulating edema); and (4) repeated intubation trauma. The subglottic region was imaged using an OCT system that produced images with axial and lateral resolution of 10 and 20 μm, respectively. The submucosal thickness (basement membrane to perichondrium) was measured in each group and compared to controls. OCT images were later correlated with conventional histology. Results: The epithelium, basement membrane, lamina propria, perichondrium, and cartilage (cricoid and tracheal) were very clearly imaged. A 50% increase in submucosal thickness was observed in group 2, and the collagen was clearly identified and distinct from surrounding native tissues. Dehydration (group 3) produced a 60% reduction while rehydrating the same specimen in distilled water resulted in a 350% increase. Edema, produced by either repeated intubation or distilled water immersion, was easily differentiated from both native and the collagen-injected tissues. Conclusion: OCT successfully identifies the layer microstructure of the subglottis and can be used to differentiate between edema and increased collagen in the rabbit model. Significance: OCT can be readily adapted for use during rigid and flexible endoscopy. Likewise, since OCT imaging fibers can be placed within endotracheal tubes to image the airway, the technique is an extremely attractive option for use in the ICU to manage the neonatal airway. Support: None reported.